If you want to know merits and costs of integrated v modular I suggest you stick those terms in the Proon search engine - its a regular topic and you will see loads of replies / arguments for and against from people more in the know than me

"fATPL Modular self improver" thread is short and contains a succinct description of both routes - don't know how to link - sorry.
but (what i remember from other peoples posts) Integrated costs £60k~ish and if you are careful, train overseas modular
can be as low as £35K.
Beast29 sorry to be the bearer of bad news but (In my opinion) I don't think your PPL will save you much. If I remember rightly a PPL is 40 odd hours (min) and depending how rusty you are it could take half that to get you up to speed again. Those 20-30 hours 'saved' would cost approx US$80 an hour (depending where you went to train - you don't need a UK PPL to get a JAA CPL - I haven't). Don't get me wrong I would rather have that money than not, but it pales into insignificance when IR/Multi training is costing £6
per minute at the end of your course